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Chapter 22 



M 134 758 

 Figure 22-5. — Types of strip flooring. (A) Side and end matched, y4-inch thick. (B) Thin 

 flooring strips, matched. (C) Thin flooring strips, square-edged. (Drawing after An- 

 derson 1970.) 



If oak flooring were manufactured from the entire product of the log, yield of 

 dry planed product would be about 28 percent of log weight, ovendry basis, 

 including bark (fig. 22-1). Normally, however, hardwood flooring manufactur- 

 ers buy specified common grades of lumber — usually 2 and 3A — which they rip 

 and crosscut to yield flooring grades desired. Flooring is graded according to 

 rules published by the National Oak Flooring Manufacturing Association 

 (1977). 



Large et al. (1971) provided data on flooring yields from northern red oak 

 kiln-dried lumber of three grades: 1, 2, and 3A Common. Each of the three 

 lumber grades was subdivided into four width-length classes. The lumber was 

 converted to tongue-and-groove flooring with 2 '/4-inch face and graded into 2 

 Common, 1 Common, Select or Clear flooring grades. Lumber grade had a 

 significant effect on both percent yield and the grade distribution of flooring. 

 One Common (IC) lumber had an overall yield of 75.5 percent followed by 2C 



